Internal combustion engine

ABSTRACT

An illustrative embodiment of a reciprocating internal combustion engine of the present invention comprises a rotatable drive shaft, a cam coupled to the rotatable drive shaft, a plurality of internal combustion cylinders symmetrically located about the drive shaft, plurality of rocker arms, each rocker arm being coupled to a piston rod of one of the cylinders, and a wheel mounted on each rocker arm and engaging the cam, whereby the rocker arm drives the cam during a power stroke while the cam drives the rocker arm during a compression stroke.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of U.S. Provisional Application No. 60/578,278, filed on Jun. 8, 2004, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

FIGS. 1A-1D depict the operation of a conventional four-stroke gasoline reciprocating internal combustion engine 100. Each cylinder of the engine comprises a cylinder 110, a piston 120, an intake port 130, an intake valve 132, an exhaust port 140, an exhaust valve 142, a spark plug 150, and a piston rod 160 connected to a crankshaft 170. A combustion chamber 180 is formed by the interior surfaces of the piston, cylinder and valves. The four strokes—intake, compression, power and exhaust—of the engine are depicted in FIGS. 1A through 1D. During the intake stroke (FIG. 1A), intake valve 132 is open and a fuel-air mixture is drawn into the combustion chamber as the piston is withdrawn by the rotating crankshaft to enlarge the combustion chamber. During the compression stroke (FIG. 1B), the valves are closed and the fuel-air mixture is compressed as the piston is pushed into the chamber by the crankshaft. The compressed fuel-air mixture is then ignited within the combustion chamber by a spark from spark plug 150. The resulting hot gases expand, driving the piston outwards (down in FIG. 1C) in the power stroke and thereby driving the crankshaft. Finally, during the exhaust stroke (FIG. 1D), the spent gases are removed from the chamber by opening exhaust valve 142 so that the piston can drive the gases out of the chamber as the piston is again pushed into the chamber by the crankshaft. In the typical automobile engine, at least four such cylinders are mounted along the crankshaft, each of which is operating at a different phase of the four-stroke cycle.

Numerous variations are well known in the design of the cylinders and in their combinations in various engines. For example, in diesel engines, the spark plug is eliminated, the compression stroke compresses pure air, and the fuel is introduced into highly compressed air. Simpler versions of the reciprocating internal combustion engine are also known. For example, the two-stroke engine uses only a compression stroke and a power stroke and eliminates much of the valve mechanisms of the four-stroke engine.

The reciprocating internal combustion engine typically operates at relatively low efficiency. Aside from thermodynamic considerations, one contributor to this inefficiency is friction between the piston and the interior wall of the cylinder. One component of this friction is the result of lateral forces exerted on the piston by the piston rod which is at an angle to the longitudinal axis of the cylinder at all times except the points of maximum compression and maximum expansion

SUMMARY OF INVENTION

An illustrative embodiment of a reciprocating internal combustion engine of the present invention comprises a rotatable drive shaft, a cam coupled to the rotatable drive shaft, a plurality of internal combustion cylinders symmetrically located about the drive shaft, a plurality of rocker arms, each rocker arm being coupled to a piston rod of one of the cylinders, and a wheel mounted on each rocker arm and engaging the cam, whereby the rocker arm drives the cam during a power stroke while the cam drives the rocker arm during a compression stroke.

BRIEF DESCRIPTION OF DRAWING

FIGS. 1A-1D are a schematic illustration of the operation of a conventional four-stroke gasoline internal combustion engine;

FIG. 2 is a schematic illustration of a first embodiment of the invention;

FIG. 3 is a schematic illustration of a second embodiment of the invention; and

FIG. 4 is a schematic illustration of a component of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

As shown in FIG. 2, a first embodiment of an engine 200 of my invention comprises a drive shaft 202, a cam 206, three internal combustion cylinders 210, 220, 230 and three rocker arms 250, 260, 270. The drive shaft, cylinders and rocker arms are mounted in a housing 280. Drive shaft 202 rotates about an axis of rotation 204 that is perpendicular to the plane of the drawing. Cam 206 is rigidly coupled to the drive shaft and rotates with it. Cylinders 210, 220, 230 each comprise a cylinder head 212, 222, 232 and a piston 213, 223, 233, the interior surfaces of which define combustion chambers 214, 224, 234, respectively. Numerous types of reciprocating internal combination cylinders may be used in the practice of the invention and many conventional details of the cylinders such as ports, valves, and spark plugs have been left out of the drawing as they are well known to those skilled in the art. Each piston 213, 223, 233 is connected to one end of a piston rod 216, 226, 236. The other end of each piston rod is connected to one end of a rocker arm. Advantageously, each piston rod is constrained by a support 217, 227, 237 so that each piston rod moves along the longitudinal axis c-c of the cylinder.

The cylinders are mounted on the housing by a mounting 218, 228, 238 in the cylinder head. The mountings are symmetrically located 120° about the axis of the drive shaft and at the same radial distance therefrom. Advantageously, the mounting permits the cylinder to be rotated over an arc of several degrees about an axis perpendicular to the plane of the drawing. As will be described more fully below, this makes it possible to adjust the stroke of the piston.

Each rocker arm 250, 260, 270 comprises a coupling 252, 262, 272 at one end that connects to a piston rod and a wheel 254, 264, 274 at the other end that engages the cam. The rocker arms are slightly bent at an elbow 256, 266, 276 near the middle of the arm and are mounted to the housing on pivots 258, 268, 278 near the elbow. The pivots permit each rocker arm to rotate about an axis of rotation perpendicular to the plane of the drawing and parallel to the axis of rotation of the drive shaft. The pivots 258, 268, 278 are symmetrically located 120° apart about the axis of the drive shaft and at the same radial distance therefrom. Biasing means schematically represented in FIG. 2 by torsion spring elements 259, 269, 279 bias the wheels of the rocker arms against the cam.

The rocker arms convert linear motion of each piston to rotary motion of the cam and driveshaft and convert rotary motion of the cam and drive shaft to linear motion of the piston. For the orientation of the pistons shown in FIG. 2, outward movement of the piston during the power stroke causes the rocker arm to which it is coupled to rotate counterclockwise and counterclockwise motion of the rocker arm causes the cam to rotate clockwise. In the case of a four-stroke engine, during the exhaust and compression strokes, the spring element causes the rocker arm to which it is attached to rotate clockwise thereby driving the piston inward in the cylinder. During the intake stroke, the cam drives the rocker arm counterclockwise and the rocker arm draws the piston outward from the cylinder. In the case of a two stroke engine, during the compression stroke, the spring element causes the rocker arm to which it is attached to rotate clockwise thereby driving the piston inward in the cylinder.

Preferably, one or more additional sets of the cylinders, rocker arms and cam shown in FIG. 2 is attached to the drive shaft at one or more other points along the axis of rotation of drive shaft 202. Preferably, the phase of each additional set is symmetrically offset from that of each of the other sets. For example, if one additional set of cylinders and rocker arms is used, the cylinder in the second set that is in the power stroke should be located at a position that is 180° away from the position of the cylinder in the first set that is in the power stroke. And if two additional sets of cylinders and rocker arms are used, the cylinders in the power stroke in the three sets should be positioned 120° away from each other. As a result, power is delivered to the cam sufficiently continuously as to provide continuous rotation of the cam and driveshaft.

As shown in FIG. 3, a second embodiment of an engine 300 of my invention comprises a drive shaft 302, a cam 306, four internal combustion cylinders 310, 320, 330, 340 and four rocker arms 350, 360, 370, 380. These elements and their operation are similar to the corresponding elements in FIG. 2. The drive shaft cylinders and rocker arms are mounted in a housing 390. Drive shaft 302 rotates about an axis of rotation 304 that is perpendicular to the plane of the drawing. Cam 306 is rigidly coupled to the drive shaft and rotates with it. Cylinders 310, 320, 330, 340 each comprise a cylinder head 312, 322, 332, 342 and a piston 313, 323, 333, 343, the interior surfaces of which define combustion chambers 314, 324, 334, 344, respectively. Again, numerous details of the cylinders such as ports, valves, and spark plugs are conventional and have been left out of the drawing as they are well known to those skilled in the art. Each piston 313, 323, 333,343 is connected to one end of a piston rod 316, 326, 336, 346. The other end of each piston rod is connected to one end of a rocker arm. Advantageously, each piston rod is constrained by a support 317, 327, 337, 347 so that each piston rod moves along the longitudinal axis c-c of the cylinder.

The cylinders are mounted on the housing by a mounting 318, 328, 338, 348 in the cylinder head. The mountings are symmetrically located 90° about the axis of the drive shaft and at the same radial distance therefrom. Advantageously, the mounting permits the cylinder to be rotated over an arc of several degrees about an axis perpendicular to the plane of the drawing. As will be described more fully below, this makes it possible to adjust the stroke of the piston.

Each rocker arm 350, 360, 370, 380 comprises a coupling 352, 362, 372, 382 at one end that connects to a piston rod and a wheel 354, 364, 374, 384 at the other end that engages the cam. The rocker arms are slightly bent at an elbow 356, 366, 376, 386 near the middle of the arm and are mounted to the housing on pivots 358, 368, 378, 388 near the elbow. The pivots permit each rocker arm to rotate about an axis of rotation perpendicular to the plane of the drawing and parallel to the axis of rotation of the drive shaft. The pivots 358, 368, 378, 388 are symmetrically located 90° apart about the axis of the drive shaft and at the same radial distance therefrom. Biasing means, schematically represented in FIG. 3 by torsion spring elements 359, 369, 379, 389 bias the wheels of the rocker arms against the cam.

The operation of the pistons, rocker arms and cam is the same as that described above in conjunction with FIG. 2 except that there are four sets of cylinders and rocker arms. Again, one or more additional sets of the cylinders, rocker arms and cam shown in FIG. 3 preferably is attached to the drive shaft at one or more other points along the axis of rotation of the drive shaft.

Wheels 254, 264, 274 of FIG. 2 and 354, 364, 374, 384 of FIG. 3 are mounted so that they will rotate in a counterclockwise direction as the rocker arms move clockwise during the compression stroke and, in the case of a four-stroke engine, the exhaust stroke. During the power stroke and, in the case of a four-stroke engine, the exhaust stroke, the wheel does not rotate so as to transfer power from the rocker arm to the cam or from the cam to the rocker arm. Advantageously, a braking mechanism (not shown) may be mounted on each rocker arm to prevent rotation during these strokes. In other cases, the pressure of the rocker arm against the cam (and vice versa in the case of a four stroke engine) may be sufficient to prevent rotation of the wheel during these strokes.

As mentioned above, the angular position of each cylinder may be changed over an arc of several degrees. As a result, the position of the piston rod in coupling 252, 262, 272 or 352, 362, 372, 382 can also be changed. Such change in position changes the leverage of the rocker arm; and, in particular, as the position of the rocker arm in the coupling is moved toward the rocker arm pivot, it reduces the length of the piston rod stroke that is required to move the rocker arm wheel a given distance. As a result, the torque available from the engine can be varied by changing the angular orientation of the cylinders and therefore the position of the piston rod in the rocker arm couplings. Advantageously, this adjustment in angular orientation of the cylinders can be made while the engine is running by an appropriate positioning mechanism mounted between each cylinder and the housing.

Alternatively, the position of the piston rod in its coupling can be adjusted by a positioning mechanism such as that shown in FIG. 4. FIG. 4 illustrates a portion of rocker arm 250 including coupling 252 to which piston rod 216 is connected. A positioning mechanism 410 is mounted on rocker arm 250 and connected by a shaft 420 to piston rod 216. Positioning mechanism 410 could be as simple as a mechanical connection that secures shaft 420 so as to fix the location of the end of piston rod 216 in coupling 252. Preferably, positioning mechanism is motor driven so as to move shaft 420 in and out and thereby move the end of piston rod 216 to a desired location in coupling 252 and retain it in that position. Advantageously, the positioning mechanism is a servo motor and the position of the piston rod can be adjusted by the servo motor while the engine is running.

As well be appreciated by those skilled in the art, numerous variations can be made in the above-described embodiments that are within the spirit and scope of my invention. 

1. An internal combustion engine comprising: a rotatable drive shaft; a cam coupled to said drive shaft and rotating with it; a first plurality of internal combustion cylinders symmetrically located about the drive shaft, each cylinder comprising a cylinder head and a movable piston that define a combustion chamber therebetween and a piston rod coupled to said piston, said piston rod moving said piston toward said cylinder head to compress a fuel-air mixture during a compression stroke and said piston moving said piston rod away from said cylinder head during an expansion stroke, and each piston rod being coupled to a rocker arm that engages the cam, whereby the rocker arm drives the cam during an expansion stroke while the cam drives the rocker arm during a compression stroke.
 2. The engine of claim 1 wherein the drive rod in each cylinder moves along a longitudinal axis of the cylinder.
 3. The engine of claim 2 wherein the longitudinal axis of each cylinder is at the same angle with a radial line from the rotatable drive shaft.
 4. The engine of claim 1 wherein each rocker arm is mounted on a pivot, the drive rod of a cylinder being coupled to the rocker arm at one end and the wheel being mounted at the other end of the rocker arm.
 5. The engine of claim 1 wherein the cylinders are two-stroke cylinders having a compression stroke and a power stroke.
 6. The engine of claim 1 wherein the cylinders are four-stroke cylinders having an intake stroke, a compression stroke, a power stroke and an exhaust stroke.
 7. The engine of claim 1 further comprising: a second plurality of internal combustion cylinders symmetrically located about the drive shaft at a position different from that at which the first plurality of cylinders is located, each cylinder comprising a cylinder head and a movable piston that define a combustion chamber therebetween and a piston rod coupled to said piston, said piston rod moving said piston toward said cylinder head to compress a fuel-air mixture during a compression stroke and said piston moving said piston rod away from said cylinder head during an expansion stroke, and each piston rod being coupled to a rocker arm on which is mounted a wheel that engages the cam, whereby the rocker arm drives the cam during an expansion stroke while the cam drives the rocker arm during a compression stroke.
 8. The engine of claim 1 wherein the position at which the piston rod is coupled to the rocker arm may be varied.
 9. The engine of claim 1 further comprising a positioning mechanism mounted on the rocker arm and coupled to the piston rod for adjusting the position at which the piston rod is coupled to the rocker arm.
 10. The engine of claim 9 wherein the positioning mechanism is a servo motor.
 11. The engine of claim 1 further comprising a wheel mounted on the rocker arm for engaging the cam. 